Filament support



Dec. 6, 1955 w JR" ET AL FILAMENT SUPPORT 2 Sheets-Sheet 1 Filed Jan. 2, 1952 I l k INVENTORS ARTHl/R If. WINGIJR- 5111500025 u. MARCHESE ATTORNEY Dec. 6, 1955 A. K. WING, JR" ET AL 2,726,349

FILANENT SUPPORT Filed Jan. 2, 1952 2 Sheets-Sheet 2 MN .2 l lllllflw lNVENTORs ARTH K. WINGJR. THEODO R /155E atent fiiice 2,726,349 lPatented Dec. 6, 1 955 FILAMENT SUPPORT Arthur K. Wing, Jr., and Theodore 33'. Marchese, Nutley,

N.'J., assignors to International Telephone and Testsgraph Corporation, a corporation of Maryland Application January 2, 1952, Serial No. 264,622 Claims. (Cl. 313-273) This invention relates to electron discharge devices and more particularly to the mechanical structure of the filament support of a directly-heated cathode type.

The basic problems encountered in prior arrangements of filament supports are that of holding an accurate alignment, both axially and spaced, of. a directly-heated cathode composed of a plurality of filamentary wires and the replacement of burned-out filamentary wires.

Having in mind these basic problems, it is an object of our invention to provide a filament support structure that lends itself to ease of fabrication and maintenance.

Another object is to provide a filament support that requires no welding of the individual filamentary wires to the mechanical support.

A-further object is to provide for each filamentary wire to beelectrically and mechanically independent, so that if. one wire becomes inoperative, the replacement of that wire may be achieved by slipping the inoperative wire out of the assembly and replacing it with a new wire merely by slipping it into the appropriate position.

The above-mentioned and other features and objects of this invention and the manner of attaining them will be best understood by reference to the following description of the embodiment of this invention taken in conjunction with the accompanying drawings, wherein:

Fig. 1 isa longitudinal cross-section view of the filament support in accordance with the principles of this invention;

Fig. 2 is an enlarged partially exploded perspective view showing in detail the upper and lower filamentary wire supporting means shown in Fig. 1; and

Fig. 3 is an enlarged perspective view showing in detail the. bifurcated filamentary wire and themanner of attaching the filamentary wire to the upper and lower supporting meansshown in Fig. 1.

Referring to Fig. 1 of the drawing, there is shown a filament support which allows for easy alignment, axial and spaced, of the directly-heated cathode with respect to they other elements of the electron discharge device and also allows for. easy removal of any inoperative filamentary Wire.

The filamentary support comprises two housing members 1 and 2. The union between these two members is accomplished by brazing member 1 to annular shoulder 4 contained ondisc 3. Disc 3 also has a circumferential groove 6 in which is placed and brazed a cylindrical metallic portion 2a. Conductor 22 and ring 47 are brazed to metallic cylinder 2e forming an integral unit. Cylinders 2a and 2e are beaded with glass after the brazing operation and are. thereafter joined together by glass seal 2b. The metallic stepped portion 2a is brazed integral to the grid supporting ring 5 and, portion is joined to metallic cylinder 2e by the glass seal 2a to finish the formation of the housing member 2. To ring 5, the grid electrode 511, only partially shown inthe drawing, is secured in a concentric relation. to the filamentary assembly. Concentric to the grid electrode 5b is situated the anode electrode which is brazed to metallic portion 5e. The stepped portion 20 has welded to it. a metallic portion. 5a. Portions 5a and 5a are beaded and joined together-by the glass seal 5d to complete that portion ofthe constructionof the tube indicated: in, the drawing. The welding of portions 2c and 5a at the point of the reference character is actually the last joint made in the assembly when the tube is finally exhausted- The housing member 1 includes an internally threaded portion 7 to receive a cap. screw 8, composedof copper if desired, which may be moved axially throughtherange allowable by the length of the threaded portion 7. This length of the threaded portion 7 must be such that a proper amount of tension may be applied to maintain the position of the plurality of bifurcated tungsten filamentary wires 9 through tension rod 10 which comprises a portion of the adjustable means for applying tension. Other portions of the tensioning means consist of'the cap screw 8 which is axially recessed to provide a seat for the larger end 11 of the annular cap screw bushing 12, which may be composed of lava or other suitable insulating and bearing material, and is secured thereto by brazing or other similar process. This larger end-11 acts as a stopfor spring 13 which is concentric with the smaller portion 14 of the annular cap screw bushing 12 and with a smaller part 15 of the annular spring stop 16 where the larger end. 17 thereof acts as a thrust element for. spring 13. The annular spring stop 16 and tension rod 10 may be composed of Monel metal and tungsten, respectively, and are joined together securely at a predetermined point by brazing or a similar process tomeet the aforementioned tension-requirement. However, the annular spring stop 16 may be machined integral. with tension rod 101 from the same piece of stock'if desired.

Tension rod. 10 which extends axially into cap' screw bushing 12 and through spring stop 16 is maintained in axial alignment by means of the inner conductor bushing 18, which may be composed of lava or other suitable insulating and bearing material. Inner conductor bushing 18 is clamped in the proper position by the bushin clamp 19 which is secured to conductor 3.

Also securedto conductor 3 in axial position therewith isan inner tubular conductor element 20 through which tension rod 10 extends. Concentric with the inner conductor element 20 there. is disposed an outer conductor element 21 supported by an annular lead conductor 22. Conductor 22 is preferably of molybdenum and has a large central aperture which receives for alignment purposes the end portion 23 of the outer conductor element 21'. Conductor 22 abuts the housing member 2 and is brazed or otherwise secured thereto. The annular flange 24 of the element 21 is also secured to conductor 22.

Referring to Figs. 2 and 3 along with Fig. 1, the details of securing filamentary wires will be more readily understandable. The lower portion of the conductor element 20 and the conductor element 21 is reduced in cross section as shown at 25' and 26, respectively, and with radially disposed. apertures 27 therein. These reduced cross sections 25 and26 with the apertures 27 are for the equalization. of thetemperatures producedby electrical energy in the respective conductor elements. -It was discovered that Without these reduced cross sections one conductor element would operate hotter than the other conductor element, thus producing, by virtue of the resulting. unequal thermal expansion, a deformation in the filamentary wires 9-,. destroying the desired axial and spaced relation. The location of the reduced cross sections 25 and 26 may be anywhere within the boundaries of their respective conductor elements but is'preferably located'as close as practicable to the filamentary wires 9 to assure temperature equalization thereof.

The lower ends of the inner conductor 20 and the outer conductor 21 incorporate radially disposed arms, as-partially shown in Fig. 2. The arms 28 located on the outer conductor element 21 are so machined that they interleave in spaced relation with arms 29 located on the inner conductor so that the bottoms thereof are flush. Through each of the arms 28 and 29 are two apertures 30 for receiving the ends 31 of the plurality of filamentary wires 9. The vertical edge of each arm contains two grooves 32 to properly position the filamentary wires 9 which extend downward therefrom. The ends 31 of the bifurcated filamentary wires 9 are bent back in such a manner that the ends 31 fit down into the apertures 30 with a portion of the filamentary wires resting in slots 32 and the remaining portion thereof extending downward to the lower filament securing means which includes discs 33 and 34. The arrangement of the wire ends 31 around the circumference of the nested arms 28 and 29 is such that one end projects into an aperture 30 in arm 28, and the other end projects into the adjacent aperture 30 in arm 29, such that the bifurcated filamentary wires 9 are connected mechanically and electrically between the conductor elements 20 and 21.

For securing the bight portion 35 of the bifurcated filamentary wires 9, the larger disc 33 includes a plurality of apertures 36 spaced adjacent the peripheral edge thereof and a plurality of peripheral vertically disposed grooves 37. The disc 33 also includes a plurality of apertures 38 coincident with a plurality of apertures 39 located in disc 34. An axial aperture 40 in disc 33 receives the end of the tension rod 10 such that a constant downward thrust, developed by spring 13 and imparted to tension rod 10, is maintained on the bifurcated filamentary wires 9 to hold them in proper spaced relation.

The bight portions 35 of the bifurcated filamentary wires 9 are bent inwardly, and the ends 41 of a plurality of bifurcated end clamps 42 project upwardly into adjacent apertures 36 after first passing through bight portion 35. The closed portion 43 of the end clamp 42 extends toward the center of the disc 33, and the disc 34 is secured tightly against closed portion 43 by means of rivets or pins 44, as shown in Fig. 1, disc 34 being secured thereto by connecting wire 45 passing through aperture 46 in the shanks of the rivets 44. Disc 34 may be secured in position by means other than that shown, for instance, by passing a wire through apertures 38 and 39.

The proper tension on the filamentary wires 9 is maintained as hereinbefore mentioned by tension rod 10 delivering a thrust developed by spring 13 to disc 33 which secures the plurality of filamentary wires 9 to the inner and outer conductor elements 20 and 21, respectively, without employing a brazing or similar process. The amount of tension applied may be adjusted by cap screw 8. If a filamentary wire 9 becomes inoperative, it is only necessary to reduce the tension by loosening the cap screw 8, loosening connection wire 45 to relieve the pressure on end clamp 42, and replacing the plurality of filamentary wires, only.

Electrical filamentary connections are provided in the electron discharge device through disc 3 and conductor 22. To achieve electrical connection to conductor 22, a metallic collar 47 is brazed or otherwise secured to the exterior of the housing member 2. The electrical path through one of the plurality of filamentary wires 9 is as follows: From metallic collar 47, one of the exterior electrical connections, through annular conductor 22 and outer conductor 21 to one of the plurality of arms 28, and then one leg of a bifurcated filamentary wire 9, with the return path through the other leg of the same bifurcated filamentary wire 9, the supporting arms 29 and the inner conductor 20 to annular conductor 3, and thence to member 1 where the other electrical connection is made.

The filament support as herein described will find use in any electron discharge device employing a directly-heated cathode, and the construction features herein enumerated may further find application in any electron discharge device whose structure may be so arranged and secured.

Although we have shown and described a specific embodiment of our invention, we are fully aware that many modifications thereof are possible. Therefore, this description is made only by way of example and not as a limitation to the scope of our invention.

We claim:

1. A filament support comprising a first tubular element and a second smaller tubular element disposed in a concentric relation with each other, a tension rod coaxial with said second tubular element, a plurality of bifurcated filamerit Wires the leg ends of which are hook-shaped, a plurality of radially projecting arms carried on one end of each of said first and second tubular elements in nested relation for support of said filament wires, each of said arms having a pair of apertures and grooves adjacent thereto for reception of the hooked-shaped ends of said filaments, and means carried by said tension rod to engage the bight end of said filaments to maintain the filaments under tension.

2. A filament support according to claim 1, wherein said means carried by said tension rod includes a first disc and a second disc, said first disc includes a plurality of apertures and a plurality of peripheral vertically disposed grooves, said second disc including a plurality of apertures coincident with a like number of said plurality of apertures in said first disc, a number of said apertures in said first disc are spaced circumferentially adjacent the peripheral edge, said number providing means securing the bight end of said filament wires, said means securing the bight end including a plurality of bifurcated clamps, the ends of said clamps extending through said bight end and upward into said number, said clamps being radially disposed therefrom and secured in position by means extending through said coincident apertures, said number cooperating with said vertically disposed grooves to maintain said filament wires in a spaced and axial relation.

3. A filament support according to claim 2, further including another one of said plurality of apertures in said first disc disposed axially to provide receptive means for said tension rod to impose a tensioning thrust thereto.

4. A filament structure comprising a first tubular element and a second smaller tubular element in a concentric relation with each other, a tension rod coaxial with said second element, one end of each of said first and said second elements having radially disposed arms in spaced alternate nested relation, a plurality of bifurcated filaments having hook-shaped ends, means including apertures and grooves in juxtaposition carried by each of said arms releasably securing the hook-shaped ends ofsaid filaments and means carried by said tension rod engaging the bight portions of said filaments to impose tension thereto.

5. A filament structure according to claim 4, wherein two of said apertures are situated adjacent the peripheral edge on each of said arms and two of said grooves are disposed on the end of each of said arms, said two of said apertures and said two of said grooves cooperating with the ends of said filaments for maintenance of a spaced and axial relation.

6. A filament structure according to claim 4, wherein said means carried by said tension rod includes a plurality of bifurcated clamps, a first disc, and a second disc, said first disc and said second disc each including a plurality of holes, a number of said plurality of holes of said first disc being disposed circumferentially on the periphery thereof for receipt of ends of said clamps after extending through said bight portion, other of said plurality of holes of said first disc coincide with said plurality of holes in said second disc to provide means securing said clamps in position, and another of said holes of said first disc being axially disposed for receipt of said tension rod, said tension rod imposing tension thereon.

7. A filament structure according to claim 4, wherein the said first and said second elements include adjacent to said radially disposed arms a reduced area and radial apertures therein for heat equalization of said first and said second elements. a

8. A filament structure according to claim 6, wherein said means securing said clamps includes binding elements extending through coincident holes of said first and said second discs.

9. A filament structure comprising a first conductor, a second conductor and a tension rod all disposed in spaced substantially parallel relation, said conductors having a plurality of arms nested together in alternate relation, a plurality of bifurcated filament wires, means contiguous said first conductor to releasably secure the end of one leg of each of said filaments to an arm of said first conductor, means contiguous said second conductor to releasably secure the end of the other leg of each of said filaments to an arm of said second conductor and means releasably securing the bight ends of said filaments to the tension rod for applying tension thereto.

10. A filament structure according to claim 9, wherein said means to releasably secure the leg ends of the filaments which are hook-shaped includes apertures disposed in said arms receiving the hooked end portions of said filaments and grooves disposed in the end portions of said arms adjacent said apertures receiving and maintaining in proper spaced relation portions of said filaments.

11. A filament structure according to claim 9, wherein said means securing the bight ends of said filaments includes a first disc, a second disc, and a pair of bifurcated clamps, said first disc contains a plurality of apertures, a number of apertures are disposed circumferentially on the periphery thereof for receipt of ends of said clamps after extending through said bight portion, other of said plurality coinciding with apertures in said second disc to provide means for securing said clamps in position, and

another of said apertures axially disposed for receipt of said tension rod for imposing tension thereto.

12. A filament structure according to claim 9, wherein the said first and the said second elements include adjacent to the lower end thereof a reduced area and radial apertures therein for heat equalization of said first and said second elements.

13. A filament structure according to claim 11, wherein said means securing said clamps includes binding elements extending through coincident apertures of said first and said second disc.

14. An electron discharge device having an envelope, a

filament support comprising first and second terminal plates carried in spaced relation by said envelope, first and second tubular elements carried respectively by said first and second terminal plates in concentric relation, each of said tubular elements having at one of its ends a plurality of radially projecting arms, the arms of said elements being nested, each arm having means to anchor the end of a filament, a tension rod disposed axially of said tubular elements, and means carried by one end of said rod to engage and apply tension to filaments anchored by said arms.

15. An electron discharge device according to claim 14, wherein said tubular elements have openings extending therethrough adjacent the arms thereof for heat equalization.

References Cited in the file of this patent UNITED STATES PATENTS 2,617,960 Kohl Nov. 11, 1952 2,693,544 Kohl Nov. 2, 1954 

